Front end shimmy and tach inaccuracy
09-16-2001, 02:44 AM
#1
Burning Brakes
Thread Starter
Front end shimmy and tach inaccuracy
Hey all!
Now that I have the new Tri Flos on my ZR-1 I am able to drive it again with some frequency. This car hasn't been driven since the ZR-1 Gathering in May. Upon starting to drive it again it's developed a shimmy in the front end. I can feel it as low as 30mph(makes me think it isn't wheel balance) but can't see it in the steering wheel until about 45mph. It gets worse til about 65 and then smooths out a bit by 71mph. Again, I can still feel it but just can't see it in the steering wheel(I can actually see the steering wheel moving one side to the other very quickly). What could it be??? Could it be a wheel out of balance, a wheel out of round, what? Something wrong with the steering rack or power steering?? I can hear the power steering pump 'groaning' when turning left with the window down. I checked the fluid level and it's fine. I've had that pump groan prob since I've owned the car and it didn't cause a shimmy before this.
My other problem is something seems to be wrong with the tach. Last year(before top end work) I was running about 73mph at 2K RPM. It seems now 2K is only 65mph. I recall when doing top end work on my '84 several years ago I somehow caused a bad ground to the tach filter which made it do all kinds of strange stuff. Thought that could be a possibility with the ZR-1 as I just had the top end off as well. Does a ZR-1 even have a tach filter? What else could cause the inaccuracy?? Thanks!
Now that I have the new Tri Flos on my ZR-1 I am able to drive it again with some frequency. This car hasn't been driven since the ZR-1 Gathering in May. Upon starting to drive it again it's developed a shimmy in the front end. I can feel it as low as 30mph(makes me think it isn't wheel balance) but can't see it in the steering wheel until about 45mph. It gets worse til about 65 and then smooths out a bit by 71mph. Again, I can still feel it but just can't see it in the steering wheel(I can actually see the steering wheel moving one side to the other very quickly). What could it be??? Could it be a wheel out of balance, a wheel out of round, what? Something wrong with the steering rack or power steering?? I can hear the power steering pump 'groaning' when turning left with the window down. I checked the fluid level and it's fine. I've had that pump groan prob since I've owned the car and it didn't cause a shimmy before this.
My other problem is something seems to be wrong with the tach. Last year(before top end work) I was running about 73mph at 2K RPM. It seems now 2K is only 65mph. I recall when doing top end work on my '84 several years ago I somehow caused a bad ground to the tach filter which made it do all kinds of strange stuff. Thought that could be a possibility with the ZR-1 as I just had the top end off as well. Does a ZR-1 even have a tach filter? What else could cause the inaccuracy?? Thanks!
09-16-2001, 10:14 AM
#2
Melting Slicks
Re: Front end shimmy and tach inaccuracy (ZR WON)
The tires have been sitting on the same patch for awhile, maybe a little driving will smooth them out.
09-16-2001, 01:27 PM
#3
Drifting
Member Since: Jul 1999
Location: Baton Rouge LA
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Re: Front end shimmy and tach inaccuracy (4cefed)
I agree with Joel, Brian.
The tires do definately take a "set".
Increase the tire pressure and put some high speed miles on them and they should be fine. Also, I find mine sensitive to pressure in general (perhaps because of the width?). I usually use 32 cold.
The tach I can't help with, except to say it is wrong.
Regards,
The tires do definately take a "set".
Increase the tire pressure and put some high speed miles on them and they should be fine. Also, I find mine sensitive to pressure in general (perhaps because of the width?). I usually use 32 cold.
The tach I can't help with, except to say it is wrong.
Regards,
09-18-2001, 03:16 AM
#4
Re: Front end shimmy and tach inaccuracy (ZR WON)
SHIMMY: First order of business is to get the tires/wheels off and have them balanced. A 'cold set' on the tires should even out after ten or twenty miles on the road, or at least be improving. If balance is okay, do a runout on the brake rotors, and general brake inspection. If runout is okay, check the wear indicator on the ball joints and the condition of the tie rod ends.
POWER STEERING GROAN: This does not sound promising. Regardless of the shimmy problem, plan on replacing the pump if this is an obvious sound at slow speed (while sitting still I'd give it a pass).
TACH: Sounds like you may have toasted something. The factory tach is hardly a precision instrument, so I wouldn't sweat it unless it is really out of whack. The ECM should let you know when you hit the 7200 RPM fuel cutoff...
Rgds,
Mark
'92 ZR-1 #032
POWER STEERING GROAN: This does not sound promising. Regardless of the shimmy problem, plan on replacing the pump if this is an obvious sound at slow speed (while sitting still I'd give it a pass).
TACH: Sounds like you may have toasted something. The factory tach is hardly a precision instrument, so I wouldn't sweat it unless it is really out of whack. The ECM should let you know when you hit the 7200 RPM fuel cutoff...
Rgds,
Mark
'92 ZR-1 #032
